High speed buffers may be used to drive switched loads, i.e., loads that require a finite amount of charge/current for a finite period of time. Loads that exhibit this behavior are generally, but are not limited to being switched-capacitor in nature.
Some high-speed buffers use an “open-loop” for driving large switched-loads. This approach can result in deviations from the desired output voltage as time and temperature change. High-gain feedback is omitted from open loop buffers due to speed limitations that ultimately can affect settling time. With open loop approaches, a speed requirement may be met, but a precision requirement may not be met.
Other high-speed buffers use a “closed-loop” in which a signal indicative of the output is compared to a reference voltage and adjustments are made to the output to match that reference voltage. Here, however, the opposite tradeoff can be the case: a precision requirement may be met, but a speed requirement may not be met.
Other circuit designs use external capacitors to help deliver charge to a switched-load. However, these designs can require additional pins and external components. This can be prohibitive in designs with low pin count requirements.